Allophycocyanin (APC) is the least-studied cyanobacterial bile-pigment invariably present within the phycobilisome core of cyanobacteria. In the present study, we describe a simple, cost-effective, and reproducible method for the purification of APC from a local isolate, Geitlerinema sp. A28DM. The pigment was extracted from the algal biomass and precipitated with 0.25% aqueous solution of the highly aromatic cationic dye “ethodin.” The precipitated APC was then subjected to a single size-exclusion chromatographic step using Sephadex G-100. Pure cyanobacterial APC (C-APC) (A652/A280 of 3.2) was obtained and characterized by its absorption spectrum with maximum at 652 nm and a shoulder at 620 nm, and by SDS-PAGE, showing two bands with molecular masses of 15 and 17.5 kDa, corresponding to α and β subunits of the biliprotein. The final yield of C-APC was 66% from its content in the crude extract. The procedure appears to be promising for wider applications and larger production of APC.